Bacteria are developing their own fight song that goes a lot like that Chumbawamba song of the late '90s: "I get knocked down, but I get up again. You're never going to keep me down."

It's a beautiful example of evolution in action. Bacteria, like all other organisms, just want to survive, so over time they adapt to their environment. Amid all the bacteria that are causing a particular illness, minor genetic differences may exist. When exposed to antibiotics, these differences may make one particular bacterium in the crew more or less susceptible to the drugs. The more susceptible bacteria die off first, and the robust ones stick around, reproducing and creating a stronger generation of bacteria that's more resistant to the antibiotics. This happens repeatedly, leaving bacteria that have evolved to overcome any antibiotic obstacle. So while a particular antibiotic treatment may kill off certain bugs today, those bacteria are evolving and that same treatment may not work tomorrow. This scenario is a reality for a growing number of different bacterial species and is resulting in superbugs causing 23,000 deaths each year in the U.S. [source: Borel].

The most common superbug that you may have heard of is a type of staph infection, methicillin-resistant Staphylococcus aureus, or MRSA. Until new treatment options were developed, this strain of staph was incredibly difficult to treat for decades. Following quickly in its tracks in developing drug resistance? Bacteria that live in the gut like Escherichia coli and Klebsiella and the bug that causes gonorrhea. One of the scariest recent examples is drug-resistant tuberculosis where alternative treatment options don't seem to work at all. Superbugs like these increasingly are forcing us to revisit the way we approach health care.